Oliver may soon discover that Arrow's revenge list may cause more harm than good-especially when it comes to his partner.

The next person on Oliver's (Stephen Amell) list is Ted Gaynor (Ben Browder), Diggle's (David Ramsey) former commanding officer and mentor from Afghanistan, who has stayed in touch over the years. Unfortunately, it also appears he has a penchant for robbing armored trucks.

"They've grown very close over the years and he's a very standup guy, but he's on the list," Ramsey tells TVGuide.com. "Diggle doesn't agree with that. Oliver and Diggle have already been at odds in terms of approaching that stuff. Oliver has seen that there are other ways to approach crime in the city, not just the list. But in this particular case, he hasn't abandoned the list altogether."

Still, though the promos show Diggle and Oliver at arrow- and gunpoint with each other, Ramsey says their relationship won't be forever damaged from this case. "Diggle will come to understand some of the trauma that Oliver has gone through and his experience on the island in a way that he hasn't really had," Ramsey says. "It leads to a deeper understanding."